Programa de Pós-Graduação em Engenharia Elétrica e de Computação
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Master Thesis Block uma ferramenta para reconhecimento e bloqueio de ataques a redes de computadores(Universidade Federal do Rio Grande do Norte, 2002) Amaral, Flávio Marcelo Cavalcante Bandeira do; Pires, Paulo Sérgio da Motta; Oliveira, Luiz Affonso Henderson Guedes de; http://lattes.cnpq.br/7987212907837941; Filho Souza, Guido Lemos de; http://lattes.cnpq.br/6614550860293610; http://lattes.cnpq.br/5093444018164760; Bezerra, João BatistaOperating Systems and hosts connected to networks can be a target for attacks. The in- creasing number and frequency of those attacks aimed at Internet connected institutions are very high as well as the risks of steal and the unauthorized access of their Information. The damage can range from a single reading to the modification of proprietary Information. NIDS, NetWork Intrusion Detection Systems, are tools used to detect attacks aimed at Online Systems. In this research, we have developed a tool named Block, which uses a free and open source NIDS to generate Cisco access lists as a response to detected attacks. Beyond authomatically blocking attacks, the developed program sends e-mail messages to the System administrator to notify about the actions taken by the tool.Master Thesis Avaliação energética e alternativas de abastecimento de energia elétrica para o setor residencial rural não eletrificado do Rio Grande do Norte(Universidade Federal do Rio Grande do Norte, 1996) Silva, Neilton Fidelis da; Souza Júnior, José Luiz de; Ramos, Francisco de Souza; Gomes, Uílsme Umbelino; http://lattes.cnpq.br/4771027087761821; Farias Júnior, Jaime Mariz de; Teixeira, Pedro Hélio GomesThe pourpose of this work is to analyse the energetical matrix, by uses and sources, of poor rural communities, and to present altematives for electrical supplying of non-electrified communities. It is also presented a financial and technological evaluation between the electrical centralized distribution system (conventional), the single wire earth retum system (SWER) and decentralized energetical altematives (biomass, solar and wind energy). The Rio Grande do Norte State has an amount of 701 registrated communities that do not dispose the electricity in their domiciles, which represents 21,925 residences. In order to contribute with changes in this so unfavorable situation for the rural sector, aggravated by social factors, this work intends to assist rural areas development decisions by the choice ofthe electification model. The actual situation ofthe energetical matrix for poor communities and a projection to a future reality were performed by the application of a questionaire to that communities, trying to identiíy their habits of consumption, structure of uses and expectation with possibilities of a future availability of electricity. This investigation allowed the knowledge of the impact of the electricity in the matrix of uses structure and a projection of electrical power demand, taking this as a basis for the design of altemative supply systems. It is also presented an evaluation of Rio Grande do Norte State energetical resources, identiíying those which represent an altemative to the centralized distribuition model, for low demografic density communities. The possibilities with solar, wind and biomass energy uses are investigated. The use of the SWER system, although it preserves the existing centralized distribution structure, is placed in the work as an altemative able to facilitate the introduction of electricity in the communities, because ofthe low cost compared with the conventional system.Master Thesis Identificação de golfinhos através de Técnicas de Processamento Inteligente de Imagens(Universidade Federal do Rio Grande do Norte, 2003-03) Magalhães, Kaiser Magalde Costa; Centeno, Tania Mezzadri; Gonçalves, Luiz Marcos Garcia; Alsina, Pablo Javier; Medeiros, Adelardo Adelino Dantas deThe inteligente processing of digital images applied to the identification of dolphins is based on several tecniques as preprocessing and segmentation of images, neural networks, mathematical morphology and geometrical transformation; they are combined to allow the dolphin images to be treated to identify different specimen. The analyzed dolphins in this work are from the S. fluviatilis species usually known as boto-cinza in Portuguese, and live in a sea area between Pipa and Tabatinga, two beaches in Rio Grande do Norte - Brazil. One of their main characteristics is a large dorsal fin. This fin acts as a dolphin identity card, since the aggressions suffered by the animal stay registered there. Another important characteristic is the own shape of the fin. In this work, we have implemented several algorithms to preprocess the image using the KLT theory and auto-contrast. We have used mathematical morphology tecniques to help extracting the characteristics and neural networks to classify the specimen. To identify the fin curvature we used two parametric cubic polynomials, associated to the two sides of the fin and both originating at the fin peak. Notches are detected at each curve and mapped to the parametric space of the polynomials. Some remarkable points are informed by the user to normalize the polynomials. The final data are maintained in a database and used to identify new images. Experimental results show that the selected characteristics are good identifiers, correctly classifying different specimens and recognizing with few errors the same specimen in different images.Master Thesis Utilização de substratos heterogêneos e planos de terra inclinados no desenvolvimento de antenas e filtros de microfita sintonizáveis(Universidade Federal do Rio Grande do Norte, 2012) Vieira, Antônio José Ferreira; D’Assunção, Adaildo Gomes; Silva, Sandro Gonçalves da; http://lattes.cnpq.br/6122570451445215; Barbin, Silvio Ernesto; http://lattes.cnpq.br/8233811412819096; http://lattes.cnpq.br/4159638862269940; http://lattes.cnpq.br/4743930013220286; Melo, Marcos Tavares de; http://lattes.cnpq.br/4933635747860906; Mendonça, Laércio Martins de; http://lattes.cnpq.br/1853488415531363This work aims to present tunable microstrip filters and antennas for applications in wireless communication systems, allowing variations in their resonant frequencies and bandwidths. Thus, in systems that present a high-intensity noise, changes in the operating frequency and bandwidth can provide higher reliability traffic of Information and improve the signal to noise ratio ofthe system. A technique was proposed to tune these devices, which consists in tilting the ground plane ofthese devices and vary the corresponding inclination angle as needed to meet the desired performances. Filters and antennas were designed using both circuit and transmission line theories combined with the tilted ground plane technique. Thereafter simulation was performed using the commercial software Ansoft-HFSS in order to validate the theoretical results. Furthermore several prototypes were built and measured using a vector network analyzer. A good agreement between measured and simulated results was observed. The obtained results showed an increase of up to 140% in the bandwidth ofthe filters and a range of up to 31% in resonant frequency of the studied antennas. Consequently by analyzing the performances of the considered microstrip devices it was observed that the application ofthe technique of tilted ground plane provides a considerable increase in the filters bandwidths and a signifícant percentage change in the resonant frequency value ofthe antennas. Therefore this technique is adequate for adjusting the response of microstrip devices with applications in filtering and electromagnetic radiation.Master Thesis Utilização de ressonadores metamateriais na melhoria de desempenho de filtros planares(Universidade Federal do Rio Grande do Norte, 2019-12-26) Silva Neto, João Alexandre da; Campos, Antônio Luiz Pereira de Siqueira; ; ; http://lattes.cnpq.br/8099257962727975; Costa, Iradilson Ferreira da; ; Rodrigues, Márcio Eduardo da Costa;This work proposes the insertion of Complementary Split-Ring Resonators (CSRR) in the planar filter ground. The intention is to improve some filter parameters found in the literature that have practical application, considering the growing demand for higher performance, smaller size, lower weight and cost of the devices that integrate the communication systems. The filters chosen were: a bandpass filter that uses Matrioska geometry for applications in the 2.45 GHz Industrial Scientific and Medical (ISM) band; and a low pass filter for digital TV applications. The idea is to insert the CSRR into the structure ground plane to increase the free attenuation of the Matrioska band-reject filter and to reduce the size of the low-pass filter. In the work the numerical and experimental results are presented, for the purpose of validation of the proposed technique. A good agreement between the results is observed, showing that the proposals presented were achieved. In the Matrioska band-reject filter, a significant improvement was obtained in the free attenuation in the filter rejection range, whereas in the low-pass filter a significant reduction in its dimensions was obtained.Doctoral Thesis Formulações explícitas para controladores preditivos generalizados: uma abordagem multiparamétrica(Universidade Federal do Rio Grande do Norte, 2019-10-30) Fonseca, Daniel Guerra Vale da; Maitelli, André Laurindo; ; ; Cavalcanti, Anderson Luiz de Oliveira; ; Dantas, André Felipe Oliveira de Azevedo; ; Dorea, Carlos Eduardo Trabuco; ; Barros, Péricles Rezende;Generalized Predictive Control (GPC) is one of the most traditional and popular Modelbased Predictive Control (MPC) techniques in industry and academia and has been applied over decades in several systems to improve the control performance. This type of controller uses process model information to predict future system behavior. In addition, GPC can deal directly with both MIMO systems and process constraints. However, when considering the constraint set, the controller needs to solve a Quadratic Programming (QP) (or a Linear Programming – LP) in real time, which can be prohibitive in certain cases, such as for embedded systems. This work uses multiparametric programming (mp) to generate an Explicit Piece-wise Affine (PWA) control law for GPC (mp-GPC) which holds the same control performance without the need to keep solving the optimization problem at each sample time. Hence, initially, the proposed formulation is compared with GPC based on online QP. The results show that the performance is maintained, reducing the computational time to calculate the control action. Then, a new format is proposed, which differs from the last one by the number of parameters needed in the mp formulation. Both propositions are applied in three different situations: a MIMO system, a process with input-output delays and a underactuated system. A comparison is made by checking the computational time spent to calculate the control signal, as well as the time required for mp resolution. Finally, studies involving a Hybrid Multiparametric GPC formulation were done , which makes use of the resolution of a multiparametric Mixed-Integer Linear Programming (mp-MILP). A nonlinear valve is used as a case study, in which its nonlinear characteristics are treated as a set of inequalities for the optimization problem, in order to minimize its effects.Doctoral Thesis Realimentação de estados baseada em regras fuzzy tipo-2 para servocontrole de sistemas não lineares(2019-12-09) Farias, Missilene da Silva; Araújo, Fábio Meneghetti Ugulino de; ; ; Maitelli, André Laurindo; ; Menezes Filho, José Bezerra de; ; Gabriel Filho, Oscar; ; Bessa, Wallace Moreira;Many researches use Takagi-Sugeno fuzzy models to accurately represent nonlinear dynamic systems. However, Takagi-Sugeno fuzzy makes the implementation of fuzzy controller more complex as system order and nonlinearities increase. Thus, the present work is aimed to overcome these limitations by using an interval type-2 fuzzy rule-based system in which the membership functions and the number of rules can be freely chosen simplifying the implementation of the technique. To this end, it is established a direct state feedback servo control to generate the nonlinear control action using parallel distributed compensation techniques with no need to include fuzzy models to describe the dynamic system. The proposed strategy is applied to a synchronous generator and also to a magnetic levitation system. From the results, it was verified that the proposed fuzzy servo control is able to stabilize the systems analyzed at different equilibrium points with higher performance and less settling times compared to the other servo controllers analyzed, given the uncertainties in the linearized model. In fact, the developed fuzzy control proved to be a proper way to accomplish this task, because fuzzy logic control itself does not depend on an accurate model.Master Thesis Análise e design de estruturas 2,5D de superfícies seletivas de frequência para aplicações em sistemas modernos de comunicações sem fio(2019-12-12) Duarte, Mychael Jales; Silva Neto, Valdemir Praxedes da; ; ; D'Assunção, Adaildo Gomes; ; D'Assunção Júnior, Adaildo Gomes; ; Vasconcelos, Cristhianne de Fátima Linhares de; ; Brito Filho, Francisco de Assis;This work presents a study on 2.5D Frequency Selective Surfaces (FSS) for applications in modern wireless communications systems. Initially, simple 2.5D patch structures are analyzed. The simple FSS are formed by square loop and Minkowski fractal-based loop. The use of the fractal curve caused a circuit miniaturization, the appearance of a new transmission band and a decrease in the bandwidth in the analyzed frequency band. The FSS 2.5D are formed from the simple structures which, for the formation of their elements, the turns were sectioned into parts, where they were printed on the upper and lower face of the dielectric and interconnected with 0.5 mm diameter cylindrical copper conductor wires. The 2.5D surfaces provided circuit miniaturization compared to fractal, without the appearance of new transmission bands in the analyzed band and without decreasing the relative bandwidth. Proving the efficiency of this miniaturization technique, three ultra-miniaturized structures for SMP (in the 1900 MHz and 2300MHz bands), Wi-Fi Halow (in the 900 MHz band) and Wi-Fi 6 (dual-band 2.45 GHz and 5.00 GHz) systems have been proposed, all three with dimensions of 10 mm x 10 mm unit cell. All FSS were stable with respect to the angle of incidence of the flat wave on the circuit surface. The simulated numerical results for the designed prototypes were obtained by the ANSYS HFSS software. The prototypes were constructed and the experimental characterization of the transmission coefficients, bandwidth and resonance frequency was performed, values obtained were compared and discussed with the results of the simulations, which showed good agreement.Master Thesis Implementação de um estimador neural de velocidade em um motor de indução trifásico(2019-12-16) Silva, Carlos Yuri Ferreira; Salazar, Andres Ortiz; ; ; Lock, Alberto Soto; ; Araújo, Fábio Meneghetti Ugulino de; ; Paiva, José Álvaro de;This work proposes to perform the speed control of an induction motor (1 cv, 2 poles, 220/380 V) without the use of a mechanical sensor attached to the rotor, avoiding some inconveniences such as a periodic maintenance and increased complexity and number of equipment are always part of the engine running. The three phase induction motor is the most used type of machine for electric drives. Low cost, construction simplicity and reliability are the motives that explains this statement. For the induction motor control was applied the control strategy known as Field Oriented Control and for the estimation of the motor rotor speed was used an artificial neural network, which observer electrical and mechanical system variables. The practical results were satisfatory, since the neural network worked for the measeured and estimated velocity, being possible to perform the control os the motor with the estimated speed in the range of 100 to 170 rad/s.Doctoral Thesis Uma arquitetura para análise de agrupamentos sobre bases de dados distribuídas(2009-03-06) Gorgônio, Flavius da Luz e; Costa, José Alfredo Ferreira; ; ; http://lattes.cnpq.br/7375286161719016; Martins, Allan de Medeiros; ; Canuto, Anne Magaly de Paula; ; Barreto, Guilherme de Alencar; ; Adeodato, Paulo Jorge Leitão;Data mining can be defined as a set of techniques for knowledge extraction and search of useful and previously unknown patterns in large multidimensional databases. Clustering is the process of discovering data clusters within high-dimensional databases, based on similarities, with a minimal knowledge of their structure. Distributed data clustering is a recent approach to deal with distributed databases, since traditional clustering algorithms require centering all databases in a single dataset. Moreover, current privacy requirements in distributed databases demand algorithms with the ability to process clustering securely. Thus, an increasing need of methods to mining data stored in a distributed way has motivated the development of algorithms to analyze each database separately and to combine the partial results to get a final result. This thesis presents a framework for cluster analysis in distributed databases using traditional algorithms, as K-means and self-organizing maps. This approach reduces significantly the amount of data transferred between remote units and the central unit. The framework includes a strategy, based on vectorial quantization, that extract a representatives subset, in order to get partial views of the existing clusters in each horizontal and/or vertical partitions of the database. Later, the representatives of each local unit are sent to the central unit, which carry out a combination of the partial results applying a clustering algorithm over all representative subsets. The experimental results with different datasets show that the framework proposed obtains results very close and with effectiveness comparable to conventional data mining techniques, where all the databases are transferred to a central unit in the pre-processing stage.